Polycycloolefin monomers, such as dicyclopentadiene norbornene, norbornadiene and other norbornene-type monomers, are known to undergo ring-opening polymerization reactions in the presence of a metathesis catalyst to form, high modulus, high impact strength polyunsaturated hydrocarbon polymers. For example, U.S. Pat. No. 4,400,340 describes the production of a poly(dicyclopentadiene) (PDCP) polymer from the metathesis catalyst ring-opening polymerizatin of dicyclopentadiene. Similarly, U.S. Pat. No. 4,568,660 describes the metathesis catalyst ring-opening copolymerization of dicyclopentadiene with such norbornene-type polycycloolefins as 1,4,5,8-dimethano-1,4,4a,5,8,8a-hexahydronaphthalene (DMHN), and 1,4,5,8-dimethano-1,4,4a,5,8,8a-octahydronaphthalene (DMON).
Such polymers, however, can be subject to degradation of their physical properties such as tensile elongation, structural integrity, modulus and impact strength due to olefin oxidation on exposure to light, heat and/or air over periods of time. Various antioxidant stabilizers have been proposed to delay such oxidation. For example, hindered phenolic and aryl amine compounds have been found useful as antioxidant stabilizing compounds for these polymers. Hindered phenolic compounds by themselves, however, have been found to be of limited effectiveness in delaying degradation of such physical properties as tensile elongation and impact strength of the polymers when incorporated therein as an antioxidant stabilizing compound, such properties exhibiting degradation after relatively short aging times. Aryl amine compounds have been found to afford some increase in protection against the loss of physical properties by oxidation of olefinic material, relative to phenolic compounds, but such degradation still proceeds within relatively short time periods. Moreover, unlike hindered phenolic compounds, some aryl amines, for example, N,N'-diphenyl-phenylenediamine, when used alone, have been found to be incompatible with polymers such as PDCP, and when incorporated therein as a stabilizing antioxidant, tend to "bleed" or otherwise migrate to the surface of such polymeric material. Such bleeding can then cause polymer discoloration and also staining of painted surfaces by further migration through the paint film.
It is an object of this invention, therefore, to provide an antioxidant stabilizing system for polymers formed from ring-opening metathesis catalyst polymerization of norbornene-type monomers such as dicyclopentadiene, tricyclopentadiene (and other oligomers of dicyclopentadiene), norbornene, norbornadiene, DMHN and DMON, and copolymers and terpolymers formed from ring-opening copolymerization of mixtures of such monomers which effectively delays degradation by olefin oxidation of such of the polymer's physical properties as mentioned above.
It is a further object of this invention to provide such an antioxidant stabilizing system which is compatible with the aforementioned polymers and which does not cause discoloration of either the polymer when incorporated therein, or of any of several paint systems which have been applied on the polymer for aesthetic purposes.